KTM 450EXC wheel bearings

[pete.ktm]

hey

just doing my rear wheel bearings. i've replaced the brake side bearing (with the circlip) and put in the spacer tube. if i knock the sprocket side bearing in all the way to the lip of the hub it's going to touch the spacer tube as the tube is about 2mm higher than the lip. that make sense?

are you sposed to guess how far to knock in the bearing so it's close but not touching the spacer?

i think last time i hammered it in too far, touched the spacer so there was pressure against the bearings so had to remove one of the bearings and replace with a new one.

whats the trick?? i'm thinking of shaving 2mm off the spacer tube but that can't be right else ktm would have done it for me.

cheers

[flyingcr250]

ive always banged mine hard on to the spacer, never had any problems.

[Jinxycat]

you need the center races hard up onto the center spacer, the center tube stops the external spacers pushing out the inside race, i wouldn't worry about the 2mm gap as long as the bearing is snug in the hub.

[pete.ktm]

if i'm banging the bearing hard in using a big socket so it only touches the outside of the bearing and the spacer is too long it's going to force the inside of the bearing out of alignment. isn't it?

[Jinxycat]

knock it in till you feel the inside race touch the tube, then stop

[pete376403]

If you hit it that hard the balls are going to break the edge off the inner and outer races. You'd be hitting it bloody hard at that point though. If you're deperately worried about it, get a long piece of threaded rod, some big flat washers and a couple of nuts. Put the rod though the centre of and use the nuts to wind the bearing in.
Are the bearings exactly the same id number as the ones you took out? Standard bearings (ie 6200 series) or some KTM exotica?

[barty5]

the spacer should only be about the same size as bearing center if you dont push in the bearing till they both meat your next post will be ( have just changed rear wheel bearing and now there is this funny rattling sound) in general once they and seal are in they will sit flush or once spacers are fitted.
Down side of not doing it this way will be incorrect spacing when you refit wheel so either it wont fit into swing arm or if it dose when you do up the axle and it all clamps up pressure will be put on bearing center to press it to where it needs to be thus trashing the bearing.

[Jinxycat]

is the other side all ok, because the bearing normaly bottoms out on the spacer at the same time it bottoms on the outer race lip, silly question, but do you have a manual?

[Jinxycat]

if you dont you can get it here http://www.ktm.com/450-EXC.72.0.html?&detailview=4&cHash=dcbf8829e1

[Jinxycat]

or not i looked and its no use :(

[pete.ktm]

after a few more hours of googling it looks like the spacer tube is sposed to be a bit longer. guess i'll try and press the bearing in so it just touchs the spacer tube. cheers guys.

----
Normal. The spacer is very slightly longer than the space in the hub that the bearings are in, thus when you tighten the axel the inner race of the bearings pinch the spacer so it is secured
----
Maybe simple to some, but install side with snap ring first because other side bottoms out against spacer, does not bottom out in hub
----
install side with snapring first. Other side bearing does NOT seat/bottom into hub.stops against inner spacer.
There is other thread with this confusion.

[Jinxycat]

your welcome, thanks for the thanks.

[camchain]

Very interesting, I had exactly the same problem & thought it was just mine. When I got my bike I noticed the sprocket side bearing was binding. Yeah, it's OK to get a little pinch on the spacer tube but 2mm-ish gap is just plain ridiculous/wrong when dealing with precision bearing fitting. The whole point is to assure perfect alignment of the parts.

I initially thought about trimming the end of the spacer tube too, but I measured everything up (ie. whole assembly relative to swingarm gap width) and decided to make a spacer to go under the bearing. Trimming tube would cause position issues with bits on sprocket side. My gap came to 1.85mm.

See attached pics, excuse my crude drawing but was just for me to figure it all out. (Drawing might make it easier for other KTM owners to see the what the story is)

Obviously a bad idea to drive a bearing in via inner race. Threaded rod an interesting idea - heaps better than bashing, but if you have a fly press you could maybe make up a bearing driver that covers both inner and outer of bearing races so you can feel it contact the spacer without getting the races misaligned, but the prob is still there every time you replace bearings.

I have no access to lathe etc, so had to make my ali spacer by hand. Bit of a hassle but worth the effort imo. This trick probably not for everyone, just what I did to suit myself.

Spacer: 48mm OD, approx 39mm ID, - 1.85mm wide.
(Definetly need to check to check individual bike for spacer width. Spacer width needs to be accurate otherwise still a problem )

[warewolf]

Not sure that filling the gap with a spacer is necessary. Every hub I've had the dubious pleasure of changing bearings has had a gap. I wonder if this is to allow for some thermal expansion or something? We did discuss this in the Adventure forum recently; someone suggested it is poor engineering but I wonder if there is some underlying reason that all brands have this, to varying degrees.

The front hub on my 640A has a big gap on EACH side. The distance between the hub's shoulder and the circlip groove is ~2mm wider than the bearing, and with that bearing hard up against the circlip there is a similar 2mm gap on the other side, between the hub and the end of the spacer. (Yes, bearings are the correct ones.)

[pete376403]

A thought - they (the original bearings) are not thrust type (angular contact thrust ball bearing is the correct term) are they? Ie a bit like taper rollers in that they can take side thrust because of the shape of the groove and therefore can only go one way around. IF they were of this type then possibly there is some sort of offset? Only take a mill each side and there's your difference.
It would be typical of KTM to use some high complexity solution.

[warewolf]

Good thought but no, just ordinary deep-groove ball bearings. The 640A sprocket carrier has a double-row angular contact bearing... fcuk is it expensive... $125 direct from SKF. In the last year or so they changed to a pair of deep-groove jobbies... cheapo solution.

[pete.ktm]

so had to make my ali spacer by hand. Bit of a hassle but worth the effort imo.


hmmm a spacer there, thats not a bad idea. BUT theres gotta be a reason, maybe it's to make sure there is a tight fit between the spacer and the inner bearing to keep water/dirt out? hope so coz the ones i took out were dry and rusty.

is it just a ktm thing, a vid i was watching was doing a yammie and he just bashed the bearings till they wern't going any further.

anyway i heated my hub enough so i could gently tap the bearing in little by little and got it just nicely seated against the end of the spacer. wheel spins just like a new one.

tomorrow it's valve adjustment time! anybody got any good tips on that, the vid on youtube makes it look pretty easy.

[warewolf]

is it just a ktm thing, a vid i was watching was doing a yammie and he just bashed the bearings till they wern't going any further.Nope; feel free to bash away until the bearing hits the inner spacer, which it should do before it hits the hub's shoulder.

[kezzafish]

all ktms i've done bearings on were as you describe pete. I've always figured the reason was to make it possible to bash the bearing out (hitting the outer race so that you don't root it) wouldn't bother with a spacer to compensate for the difference... i've always just done as you have done making sure i don't drive the bearing in too hard putting outward force on the inner race. I leave the spacer able to move freely and figure the outter spacers will move the bearings to where they are most comfortable (when you do the axel up)

[camchain]

Been thinking about this some more. Maybe they made it this way to allow for manufacturing differences. When cranking out thousands of them you'd eventually get a tolerance/binding problem if hole even fractionally not deep enough.

Making it (effectively) a blind hole means you can always guarantee a perfect bearing position - but ONLY if you install the bearing 'properly.' Still think it's a bit daft and too easy to get it wrong given that 'proper' way to drive bearing is via outer race. By the time you feel it contact the spacer tube, bearing races not perfectly aligned and stuck in this position. (Spacer tube has to be there for whole assembly to have something to tighten up to)

I've tweaked my previous post. Making a spacer washer suited me so I could easily get exactly same bearing position every time, but you'd need to be sure of dimensions (on each individual bike). Using a vernier, measuring the spacer tube is easy, but measuring hub accurately is trickier. Spacer trick probably not for everyone.

OK yeah, you can get a result just by tapping bearing in with a socket and wheel goes round and round, but I'd rather be sure bearing position is accurate every time and job simple to do.

Think maybe best solution is to just drive the bearing in with something that contacts inner and outer race.



BTW, with wheel lying flat, I pour some boiling water in the concave/cup part of hub to heat it for easy bearing extract/install.

[warewolf]

Nice trick with the water. I've bought a $20 hair drier/heat gun from the hardware shop.

I dunno that leaving the spacer loose is a good idea. That means the axle clamp load will push the inner race inboard of the outer race. If you drive the bearing via the outer race until the inner race just contacts the spacer, then the outer race could be ever so slightly inboard of the inner race. The axle clamp load will tend to bring the inner race in-line with the outer.